Method of insulator manufacture



H P LIVERSIDGE METHOD OF INSULATOR MANUFACTURE Original Filed July 22, 1915 Dec. 2 1927.

Patented Dec. 20, 1927.

UNITED STATES PATENT OFFICE.

HORAOE'IP. LIVERSIDGE, OF BALA, PENNSYLVANIA, ASSIGNOR TO ELECTRICAL DE- VELOPMENT AND MACHINE COMPANY, OF PHILADELPHIA, IIPENNSYLVANIA A.

CORPORATION.

METHOD OF INSULATOR MANUFACTURE.

Original application filed .Tu1y22, 1918, Serial No. 246,056. Divided and this application filed 7 November 14, 1925.

shrink a band or sleeve to the porcelain of an insulator, fashioning it true to the axis of the insulator for subsequent connection with a top or base, as by co-operating screw threads or other desirable mechanical 10 means.

A further purpose is to use a metal of relatively low melting point for the connecting band, preliminarily leaving the surface to which it is applied unglazed or otherwise giving it a roughened or non-cy lindrical contour. I prefer to use a metal having a low coeflicient of expansion for the band and to cast the band upon the insulator under pressure, thereby securing more intimate contact or enabling it to be cast at a lower temperature.

Further purposes will appear in the specification and in the claims.

I have preferred to illustrate my invention by but one main form thereof selecting a form which is practical and eflicient and which possesses great strength against cantilever and tensile strain and which at the same time well illustrates the principles of my invention.

Fig. 1 is a top plan view of the preferred form of my invention; V

Fig. 2 is a combined elevation and vertical central sect-ion of the construction seen in Fig. 1.;

Fig. 3 is an enlarged broken section corresponding to a part of Fig. 2;

Fig. ,4 is a broken side elevation of .an-.

other form of my invention so far as the exterior contour 1S concerned; and

Fig. 5 is a fragmentary section showing a mold used in casting.

This application is a division of my application for insulator, Serial No. 246,056, filed July 22, 1918.

In the drawings similar numerals indicate like parts. i

Uniting insulator porcelain parts to metal connections by molten metalpresents various difiiculties. V

Where the molten metal is poured directly between the parts to be united it shrinks radially in its entirety and also '10- tally away. from the outer of these parts,

- ting for it.

Serial No. 69,035.

losing the stiffening effect and strength to be had by firm contact. This I overcome by casting the metal between the insulator and an outer mold which is not the member with which it is to engage finally.

For the highest grade work the temperature must also be considered. The porcelain cannot be heated very much without reducing both its mechanical and insulating strength. With metals having a high melting pointthere is danger of injury to the porcelain due to the relatively high temper ature at which the metal must be cast which must be higher than the melting point to avoid chilling; in the attempt to avoid this there is danger of cor contact with the surface of the pores ain.

I find that the best results are attained by casting the metal against the porcelain under pressure, obtaining closer contact and better flow at the temperature selected and permitting the use of a metal having a low coefficient of expansion.

I havediscovered that there is a great ad vantage in placing the metal by which the union is to'be made about the porcelain first, before applying the outer member ultimately intended. I prefer to give the molten metal its outer finish or contour by a subsequent operation, finishing it exteriorly true .into the connection by which it is to be united with the bus bars .or with the base. I consider that I can more readily make any correction in alinement subsequent to the casting operation than during the set- However, the intended outer form can be given to the metal by the castingoperation particularly where the fastening is to be effected by a clamp.

The mechanical finish can thus be given toitvery accurately, so that the parts can be assembled in place, trueing up the bus bars with the base absolutely in whatever position of adjustment as to height the bus bars occupy. This last I have accomplished by threaded connection but obviously it can be done in other ways.

The porcelain insulator body 1 is shown as united to a connecting ring 2 at the top and to the flange 3 of a base 4: at the bottom through metal bands .5 and 6 which are cast in place between the insulator and split outer molds 7 (Figure 5) preferably [under pressure. The'bands shrink against the insulator when the metal cools. Pressure during the casting gives good contact and pressure during solidification maintains contact and also gives an effect similar toadditional shrinkage. Both are desirable though much of the benefit of my invention .can be obtained without the use of pressure. I show a split spacer 8, used during the casting for the purpose of providing an annular groove at this point.

The two ends of the insulator are suitably roughened or otherwise prepared forreeeipt of the metal bands 5 and 6 and I have shown grooves 9 for this purpose. Obviously, any roughening would serve, as the metal will closely conform to the inequalities of surface of the insulator. Leaving these surfaces of the insulator unglazed, without other roughening has been found to give good results.

I select a metal of relatively low melting point for the case band, in order that it may not crack or otherwise injure the surface of the insulator. This may be ababbitt, though I preferably use a spelter harder than babbitt for the purpose. The babbit-t and spelter both have the advanta 'e of being soft enough and yielding enough to avoid danger of crushing the porcelain during contraction. The outer metal form 7 may be heated to add its heat to that of the molten metal where the intended use of the insulator or character of material used for the band permit this additional heat to be applied.

I'Vhere specially good contact between the metal of the band and the surface of the porcelain is sought or where a higher speed of action and greater strength of support of the insulator is desired thanis obtainable with ordinary die casting I may cast under pressure or allow the metal to solidify under pressure.

The best finish for the two shrink metal bands is by external threads accurately placed with reference to the true axis of the insulator, as a support or base, as the case may be, can then be placed upon them reliably and quickly in accurate alinement, whatever the distance (i. e. height adjustment) between the two. I prefer to place the threads by a separate and subsequent operation.

The two metal bands arethreaded at 10- and 11 to co-operate with like threads upon the interior ofthe collar or ring 2 at 12 and the flange of the base at 13; The baseis also united to the insulator by a pin 14 and insulating cement 15 within a central cavity 16. The interior of the cavity 16 and the exterior of the pin are both shown as grooved, as at 17 and 18.

The collar or ring; 2 is shown as having threaded engagement with the lower frame member 19 of a bus bar clamp, which is apertured at suitable points for bolts 20. An upper frame member 21 completes the clamp for bar 22. The frame member 19 can be screwed into the collar to different distances for different heights of bus bar adjustment, and may be locked in position by screws 23, bearing upon a washer 25 In assembly, an elastic or resilient washer 25 is placed between the ring 2 or base flange, as the case may be, and an adjoi uing shoulder of the insulator body, so that the ring or base flange does not come in direct contact with the porcelain and yet is firmly supported at its edge in an axial direction by the resilient connection thus formed.

This insulator cannot get out of alinement since it cannot be put together in any other way than the way intended and the alinement is maintained, whatever the height at which the bus bar clamp is set.

The insulatin surface is divided into a flash-over flange 26 at the top and a lower creeping surface 27 of much greater length, axially. I prefer to locate the flash-over flange within approximately the upper third of the axial. length of the exposed insulator forming the lower two thirds as a relatively smooth creeping surface, free from abrupt changes of direction which would weaken it against cantilever strains and might also cause unbalanced stresses during the firing. The lower portion of the insulator should be nearly vertical forming angles in vertical planes not greater than 30 with the axis of the insulator.

The flash-over flange may be used with or without a head 28, as the slight grooving for such a head at this point is not serious.

In order to avoid danger of leakage at the bottom and also to support the outer edge of the bottom of the insulator by the base for mechanical reasons, I make the diameter of the base flange approximate that of the bottom of the exposed partof the insulator and get the best support where, as in Figure 4: the lower body portion is largest at the bottom and its outer surface substantially merges with the outer surface of the base flange.

It will be obvious that a part of the benefit of my invention may be obtained by using parts only of the structure disclosedherein and that the disclosure made will enable others skilled in the art to apply the invention in many'other forms than that shown.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent is 1. The steps in the method of unitin an the ring, thereby freeing the exterior of the r ring for attachment of the exterior connection. i

2. The steps in the method of uniting an exterior connection with a porcelain insulator, which consist in finishing a part of the surface of the porcelain insulator with a finish roughened as compared with the glaze of the remainder of the insulator, die casting a band of soft metal about such portion and in removing the exterior mold from about the band, thereby freeing the exterior of the band for attachment of the exterior connec tion.

3. The method of uniting an exterior connection to an insulator which is readily in- .jured by variation in temperature which consists in casting a band of low-fusingpoint metal about the exterior of the insulator, and subsequently uniting a fitting thereto by which the insulator may be sup ported or capped.

l. The method of securing an attaching band tightly to the exterior surface of a porcelain insulator without cracking the same, which consists in utilizing a metal for the band having a. relatively low-fusingpoint, casting the metal about the exterior surface of the insulator under pressure and in removing the mold from about the outside of the band to free it for engagement 7. The method of uniting an insulator body to an exterior connection, which consists in threading the interior of the connection, casting a band of metal about the exterior of the insulator and subsequently finishing the exterior surface of the band to fit the thread of the connection.

HORACE P. LIVERSIDGE. 

